Okay, here's some results with Snapseed-
First of all, you can use the original editing tools (Ambiance, etc.) With RAW files you just get access to an additional set of tools (called DEVELOP), which are the controls I mentioned before.
Here's what happens with the Save options:
SAVE- It basically overwrites the original embedded JPEG with a full-resolution version with your edits. Here is the trick- edits with the RAW tool set are preserved, edits with the JPEG tools are not. Depending on which tool set you select, you either get the original RAW file previewed, or the edited JPEG. It was confusing at first, but makes a lot of sense I think. The original RAW data will always be there, with your RAW tweaks as metadata. You can use the other JPEG tools, the end result is you can export a JPEG with your edits cooked in.
SAVE A COPY- Seems to basically save another RAW file, with a full resolution embedded JPEG.
EXPORT- Exports a JPEG.